Selective deposition of sioc thin films

ABSTRACT

Methods for selectively depositing silicon oxycarbide (SiOC) thin films on a dielectric surface of a substrate relative to a metal surface without generating significant overhangs of SiOC on the metal surface are provided. The methods can include at least one plasma enhanced atomic layer deposition (PEALD) cycle including alternately and sequentially contacting the substrate with a silicon precursor, a first Ar and H 2  plasma, a second Ar plasma and an etchant.

REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No.17/064,865, filed Oct. 7, 2020, which claims priority to U.S.Provisional Application No. 62/928,978, filed Oct. 31, 2019, which isincorporated by reference herein.

BACKGROUND Field

The present disclosure relates generally to the field of semiconductordevice manufacturing and, more particularly, to selective deposition ofsilicon oxycarbide (SiOC) films on dielectric materials.

Description of the Related Art

There is increasing need for dielectric materials with relatively lowdielectric constant (k) values and relatively low acid-based wet etchrates. Silicon oxycarbide (SiOC) may satisfy certain of theserequirements. Selective deposition of dielectric films like SiOC on apatterned surface, such as on a dielectric surface relative to a metalsurface can be advantageous in a number of settings. For example, in thecase of the case of self-aligned vias in Back End of Line (BEOL)processing area selective growth of a low k dielectric like SiOC on topof the existing dielectric areas of a BEOL structure is desirable.

One of the challenges with area selective deposition of dielectricmaterials such as SiOC is overgrowth on the adjacent surfaces, such ason adjacent metal areas. Such overgrowth can, for example, reduce thearea available to make a via with a low series resistance on a BEOLstructure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B show a flow diagram utilizing schematic crosssections of a portion of a substrate having first and second surfaces oflow-k material and copper, and generally illustrate area selectivedeposition in which undesirable overgrowth on the metal area is visible(FIG. 1A) and the more desirable deposition in which no depositedmaterial is present on the metal surface (FIG. 1B).

FIG. 2A and FIG. 2B show a flow diagram utilizing schematic crosssections of a portion of a substrate having first and second surfaces oflow-k material and copper, and generally illustrate an area selectivedeposition according to some embodiments utilizing a plasma treatmentand subsequent etch to remove overhangs on the copper surface.

FIG. 3 is a flow diagram illustrating a process flow for selectivelyforming a SiOC film on a dielectric surface relative to a metal surfaceaccording to some embodiments utilizing a plasma treatment andsubsequent etch to remove overhanging material from the metal surface.

FIG. 4 is a flow diagram illustrating a process flow for selectivelyforming a SiOC film on a dielectric surface relative to a metal surfaceaccording to some embodiments utilizing a plasma treatment andsubsequent etch to remove overhanging material from the metal surface.

DETAILED DESCRIPTION

Silicon oxycarbide (SiOC) films have a wide variety of applications, forexample in integrated circuit fabrication. SiOC films may be useful as,for example, etch stop layers, sacrificial layers, low-k spacers,anti-reflection layers (ARL), and passivation layers. SiOC can bedeposited selectively, for example on dielectric or low-k materialsrelative to metal, as described, for example, in U.S. application Ser.No. 16/588,600, incorporated by reference herein. This can be referredto as area selective deposition. Area selective deposition of SiOC on aflat patterned surface generally proceeds in an isotropic way, resultingin “mushroom” type growth, as is illustrated in FIG. 1A. The depositedmaterial typically grows both vertically and horizontally from the areain which the growth selectively takes place. In many applications thislateral growth is undesirable. Vertical growth is preferred to maintainthe dimension of the original structure on which the growth takes placeand not to cover the neighboring area, as is shown in FIG. 1B.

In some embodiments, area selective growth of a dielectric, for examplea low k dielectric such as SiOC, takes place selectively on a firstsurface, such as a dielectric or low-k surface, without undesirablelevels of overgrowth on a second surface, such as a metal surface. Insome embodiments the first surface comprises an inorganic dielectricsurface, such as low-k material, while the second surface comprises ametallic surface, such as an elemental metal or metal alloy. Examples oflow-k material include silicon oxide-based materials, including grown ordeposited silicon dioxide, doped and/or porous oxides, native oxide onsilicon, etc. In some embodiments, area selective deposition of adielectric is conducted using a PEALD process that includes one or moreplasma treatment and/or etch steps that preferentially remove materialgrown laterally over a neighboring metal surface. In some embodiments awet etch, such as in dilute HF, and/or a dry etch may be utilized in theprocess to remove SiOC from adjacent metal surfaces and obtain a desiredstructure.

In some embodiments SiOC is selectively deposited on a dielectricsurface of a substrate relative to a different surface of the substrate,such as a metal surface. For example, SiOC may be preferentiallydeposited on dielectrics like SiO₂ or SiN relative to metals like TiN,W, Co, Cu, or Ru. In some embodiments the area selective PEALDdeposition process can be a SiOC deposition process using(3-methoxypropyl) trimethoxysilane (MPTMS) as a silicon precursor and ahydrogen plasma reactant. The deposition conditions may be selected suchthat the top surface of the SiOC has a lower etch rate than the SiOC onthe sidewalls. For example, the plasma used in the reaction with thesilicon precursor may be anisotropic and can result in inhomogeneouscharacteristics of the deposited material. The wet etch rate of SiO2,SiN or SiOC in diluted HF is known to be very sensitive to e.g. thedensity of the material and the hydrogen impurity content in thematerial, which depend on how direct the grown material is exposed tothe plasm ions. The top surface is directly exposed to the ions of theincoming plasma, while the material at the sidewall is more indirectlyexposed to the plasma. Thus, the plasma used to react with the siliconprecursor to form SiOC can be tuned in such a way that the top surfaceof the deposited SiOC has a low wet etch rate, while material on thesidewall has a higher wet etch rate.

The material at the side of the overhang on the metal surface, alsoreferred to as the “mushroom” shape is less directly exposed to theincoming plasma and as a result, the portion of the film that overhangsthe metal surface will generally have a higher etch rate than theportion of the film overlying the dielectric material. Thischaracteristic can be used to etch and reshape the area selectivelygrown material by preferentially etching away the material that is grownlaterally over the neighboring metal surface, as is depicted in FIG. 2B.The deposition process may include a plasma treatment that removesmaterial preferentially from an overhanging portion on the metalsurface. The deposition process may also include an etching process,such as a diluted wet etch, and/or a dry or plasma etch to removedeposited SiOC from over the metal surface. The entire process can beperformed in a cyclic manner, repeating several deposition and etchcycles. The result is a structure with a minimal amount of lateralgrowth over the neighboring metal surfaces, as illustrated in FIG. 2B.

The PEALD processes for selectively forming a SiOC film on a dielectricsurface relative to a metal surface may be used in a variety ofapplications. In some embodiments the processes are used in various backend of line (BEOL) or middle-of-line (MOL) applications. For example, aPEALD process as described herein may be used in the formation of low-kdielectric layers on top of existing dielectric material in theformation of a back end of line (BEOL) structure.

According to some embodiments methods for selectively forming SiOC filmson dielectric or low-k surface relative to metal surfaces are provided.In some embodiments SiOC on the metal surface is reduced relative toSiOC on the dielectric surface or avoided completely. In someembodiments SiOC thin films are formed on a first dielectric surface ofa substrate relative to a second metal surface by plasma-enhanced atomiclayer deposition (PEALD) processes. In some embodiments SiOC thin filmsare not deposited by liquid phase methods. According to some embodimentsmethods for selectively forming SiOC films on a first surface relativeto a second surface, wherein the first and second surfaces are differentfrom each other, are provided.

The formula of the silicon oxycarbide films is generally referred toherein as SiOC for convenience and simplicity. As used herein, SiOC isnot intended to limit, restrict, or define the bonding or chemicalstate, for example the oxidation state of any of Si, O, C, and/or anyother element in the film. Further, in some embodiments SiOC thin filmsmay comprise one or more elements in addition to Si, O, and/or C, suchas S. In some embodiments the SiOC films may comprise Si—C bonds and/orSi—O bonds. In some embodiments the SiOC films may comprise Si—C bondsand Si—O bonds and may not comprise Si—N bonds. In some embodiments theSiOC films may comprise Si—S bonds in addition to Si—C and/or Si—Obonds. In some embodiments the SiOC films may comprise more Si—O bondsthan Si—C bonds, for example a ratio of Si—O bonds to Si—C bonds may befrom about 1:1 to about 10:1. In some embodiments the SiOC may comprisefrom about 0% to about 40% carbon on an atomic basis. In someembodiments the SiOC may comprise from about 0.1% to about 40%, fromabout 0.5% to about 30%, from about 1% to about 30%, or from about 5% toabout 20% carbon on an atomic basis. In some embodiments the SiOC filmsmay comprise from about 0% to about 70% oxygen on an atomic basis. Insome embodiments the SiOC may comprise from about 10% to about 70%, fromabout 15% to about 50%, or from about 20% to about 40% oxygen on anatomic basis. In some embodiments the SiOC films may comprise about 0%to about 50% silicon on an atomic basis. In some embodiments the SiOCmay comprise from about 10% to about 50%, from about 15% to about 40%,or from about 20% to about 35% silicon on an atomic basis. In someembodiments the SiOC may comprise from about 0.1% to about 40%, fromabout 0.5% to about 30%, from about 1% to about 30%, or from about 5% toabout 20% sulfur on an atomic basis. In some embodiments the SiOC filmsmay not comprise nitrogen. In some other embodiments the SiOC films maycomprise from about 0% to about 5% nitrogen on an atomic basis (at %).

ALD-type processes are based on controlled, generally self-limitingsurface reactions. Gas phase reactions are typically avoided bycontacting the substrate alternately and sequentially with thereactants. Vapor phase reactants are separated from each other in thereaction chamber, for example, by removing excess reactants and/orreactant byproducts between reactant pulses. The reactants may beremoved from proximity with the substrate surface with the aid of apurge gas and/or vacuum. In some embodiments, excess reactants and/orreactant byproducts are removed from the reaction space by purging, forexample with an inert gas.

In some embodiments, plasma enhanced ALD (PEALD) processes are used toselectively form SiOC films on a dielectric surface relative to a metalsurface. Selectivity of deposition on a first surface A relative tosecond surface B can be given as a percentage calculated by [(depositionon surface A)−(deposition on surface B)]/(deposition on the surface A).Deposition can be measured in any of a variety of ways known in the artor as described herein. For example, deposition may be given as themeasured thickness of the deposited material or may be given as themeasured amount of material deposited. In some embodiments selectivityof formation of SiOC on a first surface relative to a second surface,such as on a dielectric surface relative to a metal surfaceis >20%, >25%, >50%, >80%, >90%, >93%, >95%, >97%, >98%, or even greaterthan >99%.

The deposition process may include the use of plasma to form the SiOC,as well as a plasma treatment and subsequent etch treatment to removeSiOC that has been formed on the metal surface and thereby enhance theselectivity. The plasma conditions in the deposition process may beselected to achieve a desired etch selectivity in the deposited SiOC andto facilitate the removal of SiOC that has undesirably formed on themetal surface.

In some embodiments, thin SiOC films are selectively formed on thedielectric surface of a substrate relative to a metal surface byrepetition of a PEALD cycle. In some embodiments for forming SiOC films,each PEALD cycle comprises at least four distinct phases. An exemplarycycle 100 for selectively forming SiOC on a dielectric surface relativeto a metal surface is illustrated in FIG. 3. Briefly, a substrate orworkpiece comprising a dielectric surface and a metal surface is placedin a reaction chamber and subjected to alternately repeated surfacereactions. In a first phase (110, 120), a vapor phase first reactant orprecursor comprising silicon contacts the substrate 110 and forms nomore than about one monolayer of silicon species on the substratesurface. This reactant is also referred to herein as “the siliconprecursor,” “silicon-containing precursor,” or “silicon reactant” andmay be, for example, a silicon precursor comprising organic ligands or asilicon precursor comprising Si—O bonds. In some embodiments the siliconprecursor comprises 3-methoxypropyltrimethoxysilane (MPTMS) orbis(triethoxysilyl)ethane (BTESE). The deposition conditions, such asthe temperature, are selected such that species of the first reactantadsorb preferentially on the dielectric surface of the substraterelative to the metal surface.

The first silicon reactant pulse can be supplied in gaseous form. Thesilicon precursor gas is considered “volatile” for purposes of thepresent description if the species exhibits sufficient vapor pressureunder the process conditions to transport the species to the substratesurface in sufficient concentration to saturate exposed surfaces.

In some embodiments the silicon reactant contacts the substrate surfacefor about 0.05 seconds to about 5.0 seconds, about 0.1 seconds to about3 seconds or about 0.2 seconds to about 1.0 seconds. The optimumcontacting time can be determined by the skilled artisan based on theparticular circumstances.

In some embodiments excess first vapor phase reactant and any reactionbyproducts are subsequently removed from the proximity of the substratesurface 120. The first vapor phase reactant and any reaction byproductsmay be removed from proximity with the substrate surface with the aid ofa purge gas and/or vacuum. In some embodiments, excess reactant and/orreactant byproducts are removed from the reaction space by purging, forexample with an inert gas. The removal may, in some embodiments, becarried out for about 0.1 seconds to about 10 seconds, about 0.1 secondsto about 4 seconds or about 0.1 seconds to about 0.5 seconds. In someembodiments the substrate may be moved in order to facilitate removal ofthe reactant and/or reactant byproducts from the vicinity of thesubstrate surface, for example by moving the substrate to a differentreaction chamber or a separate portion of the reaction chamber.

In a second phase (130, 140), a second reactant comprising a reactivespecies from a plasma contacts the substrate and converts adsorbedsilicon species to SiOC 130, such that SiOC is preferentially depositedon the dielectric surface relative to the metal surface. Some depositionmay, however, occur on the metal surface, for example as illustratedschematically in FIG. 1A. The first phase and second phase (110, 120,130, 140) may together be referred to as the SiOC deposition portion ofthe overall cycle 100.

The second reactant may comprise a hydrogen precursor and may comprise areactive hydrogen species. In some embodiments a reactive speciesincludes, but is not limited to, radicals, plasmas, and/or excited atomsor species. Such reactive species may be generated by, for example,plasma discharge, hot-wire, or other suitable methods. In someembodiments the reactive species may be generated remotely from thereaction chamber, for example up-stream from the reaction chamber(“remote plasma”). In some embodiments the reactive species may begenerated in the reaction chamber, in the direct vicinity of thesubstrate, or directly above the substrate (“direct plasma”).

The second reactant may comprise other species that are not hydrogenspecies. In some embodiments, the second reactant may comprise reactivespecies from a noble gas, such as one or more of He, Ne, Ar, Kr, or Xe,for example as radicals, in plasma form, or in elemental form. In someembodiments the second reactant comprises reactive species from an Arplasma. These reactive species from noble gases do not necessarilycontribute material to the deposited film but can in some circumstancescontribute to film growth as well as help in the formation and ignitionof plasma.

In some embodiments the substrate is contacted with a reactantcomprising H₂ and Ar plasma. The plasma, such as hydrogen and argonplasma may be formed by generating a plasma in a reactant gas, such ashydrogen and argon gas, in the reaction chamber or upstream of thereaction chamber, for example by flowing the hydrogen (H₂) and Arthrough a remote plasma generator.

In some embodiments one or more gases that are used to form a plasma mayflow constantly throughout the deposition process but only be activatedintermittently. For example, H₂ and/or Ar gas may flow continuouslythroughout the deposition process. In some embodiments the gas may serveas a carrier gas for the silicon reactant and as a plasma reactant.

In some embodiments, the second reactant comprises plasma generated inflowing H₂ and Ar gas. In some embodiments H₂ and Ar containing gas isprovided to the reaction chamber before the plasma is ignited. In someembodiments the H₂ and Ar gas is provided to the reaction chambercontinuously and hydrogen and argon containing plasma is created orsupplied when needed. In some embodiments also in addition to H₂ and/orAr, N₂ is provided to the reaction chamber before the plasma is ignited.In some embodiments also only N₂ is provided to the reaction chamberbefore the plasma is ignited.

In some embodiments the second reactant may be generated from a gascontaining more than about 1 atomic % (at %) hydrogen, more than about10 atomic % (at %) hydrogen more than about 25 atomic % (at %) hydrogen,more than about 25 atomic % (at %) hydrogen, more than about 50 at %hydrogen, more than about 75 at % hydrogen, more than about 85 at %hydrogen, more than about 90 at % hydrogen, more than about 95 at %hydrogen, more than about 96 at %, 97 at %, 98 at %, or more than about99 at % hydrogen.

In some embodiments the second reactant may be generated from a gascontaining more than about 1 atomic % (at %) argon, more than about 10atomic % (at %) argon more than about 25 atomic % (at %) argon, morethan about 25 atomic % (at %) argon, more than about 50 at % argon, morethan about 75 at % argon, more than about 85 at % argon, more than about90 at % argon, more than about 95 at % argon, more than about 96 at %,97 at %, 98 at %, or more than about 99 at % argon.

Typically, the second reactant, for example hydrogen and argon plasma,contacts the substrate for about 0.1 seconds to about 10 seconds. Insome embodiments the second reactant, such as hydrogen and argon plasma,contacts the substrate for about 0.1 seconds to about 10 seconds, 0.5seconds to about 5 seconds or 0.5 seconds to about 2.0 seconds. However,depending on the reactor type, substrate type and its surface area, thesecond reactant contacting time may be even higher than about 10seconds. In some embodiments, contacting times can be on the order ofminutes. The optimum contacting time can be readily determined by theskilled artisan based on the particular circumstances.

In some embodiments the second reactant is provided in two or moredistinct pulses, without introducing another reactant in between any ofthe two or more pulses. For example, in some embodiments a plasma, suchas a hydrogen and argon plasma, is provided in two or more sequentialpulses, without introducing a Si-precursor in between the sequentialpulses. In some embodiments two or more sequential plasma pulses aregenerated by providing a plasma discharge for a first period of time,extinguishing the plasma discharge for a second period of time, forexample from about 0.1 seconds to about 10 seconds, from about 0.5seconds to about 5 seconds or about 1.0 seconds to about 4.0 seconds,and exciting it again for a third period of time before introduction ofanother precursor or a removal step, such as before the Si-precursor ora purge step. Additional pulses of plasma can be introduced in the sameway. In some embodiments a plasma is ignited for an equivalent period oftime in each of the pulses.

In some embodiments a gas that is used to form a plasma does notcomprise oxygen. In some embodiments the adsorbed silicon precursor isnot contacted with a reactive species generated by a plasma from oxygen.In some embodiments a second reactant comprising reactive species isgenerated in a gas that does not comprise oxygen. For example, in someembodiments a second reactant may comprise a plasma generated in a gasthat does not comprise oxygen. In some embodiments the second reactantmay be generated in a gas comprising less than about 50 atomic % (at %)oxygen, less than about 30 at % oxygen, less than about 10 at % oxygen,less than about 5 at % oxygen, less than about 1 at % oxygen, less thanabout 0.1 at % oxygen, less than about 0.01 at % oxygen, or less thanabout 0.001 at % oxygen.

In some embodiments a gas that is used to form a plasma does notcomprise nitrogen. In some embodiments the adsorbed silicon precursor isnot contacted with a reactive species generated by a plasma fromnitrogen. In some embodiments a second reactant comprising reactivespecies is generated in a gas that does not comprise nitrogen. Forexample, in some embodiments a second reactant may comprise a plasmagenerated in a gas that does not comprise nitrogen. However, in someembodiments a gas that is used to form a plasma may comprise nitrogen.In some other embodiments the second reactant may comprise nitrogenradicals, nitrogen atoms and/or nitrogen plasma. In some embodiments thesecond reactant may be generated in a gas comprising less than about 25atomic % (at %) nitrogen, less than about 20 at % nitrogen, less thanabout 15 at % nitrogen, less than about 10 at % nitrogen, less thanabout 5 at % nitrogen, less than about 1 at % nitrogen, less than about0.1 at % nitrogen, less than about 0.01 at % nitrogen, or less thanabout 0.001 at % nitrogen. In some embodiments the second reactant maybe generated in a gas comprising hydrogen and nitrogen, for example thesecond reactant may comprise H₂ and N₂. In some embodiments the secondreactant may be generated in a gas having a ratio of N₂ to H₂ (N₂/H₂) ofless than about 20%, less than about 10%, or less than about 5%.

In some embodiments a gas that is used to form a plasma does notcomprise nitrogen or oxygen. In some embodiments the adsorbed siliconprecursor is not contacted with a reactive species generated by a plasmafrom nitrogen or oxygen. In some embodiments a second reactantcomprising reactive species is generated in a gas that does not comprisenitrogen or oxygen. For example, in some embodiments a second reactantmay comprise a plasma generated in a gas that does not comprise nitrogenor oxygen.

In some embodiments the plasma is anisotropic. In some embodiments theplasma power, composition and reaction parameters are tuned such thatthe SiOC is deposited selectively on the dielectric surface relative tothe metal surface and has desired etch rate characteristics. Inparticular, in some embodiments SiOC deposited on a dielectric surfacehas different characteristics from SiOC that may be deposited on metalsurfaces. For example, SiOC that is selectively deposited on adielectric surface may have higher density and lower etch rates thanSiOC that is deposited on a metal surface during the same depositionprocess. In some embodiments horizontal or top surfaces of a depositedSiOC film have a lower etch rate, such as a lower wet etch rate indilute HF, than the non-horizontal or sidewall surface of the same SiOCfilm. As discussed herein, these differential properties can be used topreferentially etch SiOC from the metal surface and create a desireddeposition profile.

In some embodiments, the second reactant may be free or substantiallyfree of oxygen-containing species (e.g., oxygen ions, radicals, atomicoxygen). In some embodiments, the second reactant does not comprise anyspecies generated from nitrogen.

In some embodiments the plasma power, plasma composition and/or thetemperature of the susceptor is tuned to achieve desired selectivity anddesired etch rate characteristics in the deposited SiOC film.

In some embodiments the plasma power is tuned to achieve selectivedeposition of SiOC on a dielectric surface relative to a metal surface.In some embodiments the plasma power is tuned such that SiOC depositedon the metal surface has a higher etch rate than the SiOC deposited onthe dielectric surface. In some embodiments, a plasma power used forgenerating a second reactant plasma can be about 5 Watts (W) to about5000 W, 10 W to about 2,000 W, about 50 W to about 1000 W, about 100 Wto about 1000 W or about 100 W to about 500 W. In some embodiments, aplasma power can be about 100 W to about 300 W.

In some embodiments the temperature of the susceptor supporting thesubstrate may be selected to achieve the desired selective deposition ofSiOC on a dielectric surface relative to a metal surface and to achievethe desired etch rate characteristics in the SiOC on the differentsurfaces. In some embodiments the temperature is selected such that SiOCthat is formed on a dielectric surface has a lower etch rate than SiOCthat is formed on a metal surface by the same process. In someembodiments the susceptor temperature is from about 20 to about 700 C,from about 50 to about 600 C, from about 100 to about 550 C or fromabout 200 to 500 C.

In some embodiments the amount of each of H₂ and Ar in the gas in whichthe plasma is generated is selected to achieve the desired selectivityand etch rate characteristics in the SiOC. In some embodiments the H/Rratio is less than 1:1 but not 0:1, less than about 1:2 but not 0:1,less than about 1:5 but not 0:1, less than about 1:10 but not 0:1 orless than about 1:20, but not 0:1.

In some embodiments excess second reactant and any reaction byproductsare removed 140 from the proximity of the substrate surface. The secondreactant and any reaction byproducts may be removed from proximity withthe substrate surface with the aid of a purge gas and/or vacuum. In someembodiments, excess reactant and/or reactant byproducts are removed fromthe reaction space by purging, for example with an inert gas. Theremoval may, in some embodiments, be carried out for about 0.1 secondsto about 10 seconds, about 0.1 seconds to about 4 seconds or about 0.1seconds to about 0.5 seconds. In some embodiments the substrate may bemoved in order to facilitate removal of the reactant and/or reactantbyproducts, for example by moving the substrate to a different reactionchamber or a separate portion of the reaction chamber.

The first and second phases (110, 120, 130, 140), the SiOC depositionportion of the deposition cycle, may be repeated 180 one, two or moretimes consecutively prior to beginning the third (150, 160) and/orfourth (170) phase of the entire SiOC formation cycle 100. For example,the first and second phases may be repeated until a SiOC layer of adesired thickness has been formed on the dielectric surface.

While the SiOC deposition is selective on the dielectric or low-ksurface relative to the metal surface, in some embodiments overhangs ofSiOC may be present on the metal surface. This is illustrated in FIG.2A, which shows the deposition of SiOC on a low-k material relative tocopper, with the formation of overhangs of SiOC on the copper surface.The overhangs may be reduced or eliminated by including the third and/orfourth phases, as described below, in one or more deposition cycles.

Although referred to as the first phase and second phase, in someembodiments for forming a SiOC film, one or more SiOC deposition cycles100 begins with the first phase by contacting the substrate with thesilicon precursor, followed by the second precursor. In otherembodiments one or more SiOC deposition cycles 100 may begin with thesecond phase by contacting the substrate with the second reactant,followed by the silicon precursor.

In a third phase (150, 160), the substrate may be contacted 150 with areactant comprising a plasma. For example, the substrate may becontacted with a plasma generated in a noble gas, such as Ar plasma. Insome embodiments the plasma is directional, and preferentially attacksSiOC that has been formed on the metal surface relative to SiOC that hasbeen formed on the dielectric surface. This is illustrated in theright-hand panel of FIG. 2A, where the arrows represent the plasmatreatment of the surfaces.

Plasma power and duration can be tuned to increase the preferentialtargeting of the SiOC overhangs on the metal surface. In someembodiments the third phase preferentially removes SiOC from the metalsurface relative to the dielectric surface.

In some embodiments excess third reactant and reaction byproducts may beremoved from the proximity of the substrate surface 160, such as withthe aid of a purge gas and/or vacuum, or by moving the substrate to adifferent reaction chamber or a separate portion of the reactionchamber. The removal may, in some embodiments, be carried out for about0.1 seconds to about 10 seconds, about 0.1 seconds to about 4 seconds orabout 0.1 seconds to about 0.5 seconds. The third phase may be repeated190 two or more times in each complete deposition cycle 100. In someembodiments the third phase may be included in each deposition cycle. Insome embodiments the third phase is not included in every depositioncycle but is provided one or more times in the deposition process.

An optional fourth phase (170) may be included to further etch SiOC fromthe metal surface, for example if it is not removed to a desired extentin the third phase. In the fourth phase, the substrate is contacted withan etchant 170 to preferentially remove SiOC from over the metal surfacerelative to the dielectric surface. This is illustrated in FIG. 2B,which shows the preferential etching of the overhangs relative to thetop surface of the deposited SiOC film. In some embodiments the etchantis directional. The fourth phase may be included in the SiOC formationcycle 100, for example, if the plasma treatment in the third phase isnot sufficient to achieve the desired level of removal of SiOC overhangsfrom the metal surface. The fourth phase may be included in every cycle100. In some embodiments the fourth phase is not included in every cycle100 but is provided one or more times in the SiOC deposition process.For example, the fourth phase may be included after a certain number ofrepetitions of a cycle that includes only the first three phases, suchas after every one, two, three, four, five or more such depositioncycles.

In some embodiments the etchant may be a reactive gas, such as areactive halide gas such as CF₄, SF₆, HF, Cl₂ or NF₃. In someembodiments a wet etch is used to preferentially remove the SiOCoverhangs from the metal surface. For example, etching in dilute HF maybe used to preferentially remove SiOC from the metal surface. Theetchant preferentially removes SiOC from the metal surface, leaving adesired SiOC structure on the dielectric surface, for example asillustrated in FIG. 2B.

In some embodiments, the etchant may comprise, for example, a plasmagenerated in a halide gas such as CF₄, SF₆, HF, Cl₂ or NF₃. The plasmapower and time may be selected to achieve the desired amount of etching.The etching plasma may be directional. The etching plasma preferentiallyattacks the SiOC on the metal surface relative to the bulk portion ofthe SiOC deposited on the dielectric surface, leaving a desiredstructure as illustrated in FIG. 2B.

Additional phases may be added and phases may be removed as desired toadjust the composition and selectivity of the SiOC film.

The entire SiOC formation cycle may be repeated 200 two, three or moretimes to achieve a desired amount of SiOC on the metal surface relativeto the dielectric surface.

In some embodiments, two of the phases may overlap, or be combined. Forexample, the silicon precursor and the second reactant may contact thesubstrate simultaneously in phases that partially or completely overlap.In addition, the order of the phases may be varied, and an ALD cycle maybegin with any one of the phases. That is, unless specified otherwise,the reactants can contact the substrate in any order, and the processmay begin with any of the reactants.

A complete PEALD cycle according to some embodiments may be written as:

[Si reactant+Ar/H₂ plasma]×N+[Ar plasma]×M+[Etchant]×Y, where N, M and Yare integers that can be selected independently. In some embodiments anyof N, M and Y may be zero in one or more deposition cycles in a completedeposition process.

The selective SiOC deposition takes place on a substrate in a reactionspace or reactor. In some embodiments each of the four phases takesplace in the same reaction space and/or reactor. The reactor may be partof a cluster tool in which a variety of different processes in theformation of an integrated circuit are carried out. In some embodimentsa flow-type reactor is utilized. In some embodiments a shower head typeof reactor is utilized. In some embodiments, a space-divided reactor isutilized. In some embodiments a high-volume manufacturing-capable singlewafer ALD reactor is used. In other embodiments a batch reactorcomprising multiple substrates is used. For embodiments in which batchALD reactors are used, the number of substrates may be in the range of10 to 200, in the range of 50 to 150, or in the range of 100 to 130.

In some embodiments, if necessary, the exposed surfaces of the substratecan be pretreated to provide reactive sites to react with the firstphase of the ALD process. In some embodiments a separate pretreatmentstep is not required. In some embodiments the substrate is pretreated toprovide a desired surface termination on one or more surfaces. Forexample, the substrate may be treated to provide surface terminations onthe dielectric surface to enhance selectivity. In some embodiments thesubstrate may be treated to provide a blocking or passivation layer onthe metal surface to increase selectivity of the deposition on thedielectric surface.

As mentioned above, in some embodiments a gas is provided to thereaction chamber continuously during one or more phases of thedeposition cycle, or during the entire deposition cycle, or eventhroughout the entire deposition process. Reactive species may beprovided by generating a plasma in a gas, either in the reaction chamberor upstream of the reaction chamber. In some embodiments the gas doesnot comprise nitrogen. In some embodiments the gas may comprise a noblegas, such as argon or helium. In some embodiments the gas is argon. Theflowing gas may also serve as a purge gas. For example, flowing argonmay serve as a purge gas for a first silicon precursor and also serve asa source of reactive species second reactant and a third reactant (as asource of reactive species). In some embodiments, argon may serve as apurge gas for a first precursor and a source of excited species forconverting the silicon precursor to the SiOC film and as the source ofreactive species for a plasma treatment, such as in the second and thirdphases described above.

In some embodiments the deposition parameters, such as the precursorflow rate, contacting time, removal time, reactants themselves, plasmapower, reaction chamber temperature and susceptor temperature may beselected in order to selectively form a SiOC film with the desiredcharacteristics on a dielectric surface relative to a metal surface. Inparticular, one or more of these parameters may be selected to reduce,minimize or prevent deposition of SiOC on a metal surface of thesubstrate and/or to preferentially remove SiOC from the metal surface.

In some embodiments plasma, for example hydrogen and argon containingplasma, argon plasma, or etching plasma may be generated by applying RFpower of from about 5 W to about 5000 W, 10 W to about 2000 W, fromabout 50 W to about 1000 W, or from about 200 W to about 800 W. In someembodiments the RF power density may be from about 0.02 W/cm² to about2.0 W/cm², or from about 0.05 W/cm² to about 1.5 W/cm². The RF power maybe applied to a reactant gas that flows during the plasma contactingtime, that flows continuously through the reaction chamber, and/or thatflows through a remote plasma generator. Thus, in some embodiments theplasma is generated in situ, while in other embodiments the plasma isgenerated remotely. In some embodiments a showerhead reactor is utilizedand plasma is generated between a susceptor (on top of which thesubstrate is located) and a showerhead plate. In some embodiments thegap between the susceptor and showerhead plate is from about 0.1 cm toabout 20 cm, from about 0.5 cm to about 5 cm, or from about 0.8 cm toabout 3.0 cm.

According to some embodiments, the PEALD reactions may be performed attemperatures ranging from about 25° C. to about 700° C., from about 50°C. to about 600° C., from about 100° C. to about 450° C., or from about200° C. to about 400° C. In some embodiments, the optimum reactortemperature may be limited by the maximum allowed thermal budget.Therefore, in some embodiments the reaction temperature is from about100° C. to about 300° C. In some applications, the maximum temperatureis around about 200° C., and, therefore the PEALD process is run at thatreaction temperature. In some embodiments the susceptor temperature isthe same as the reaction space temperature. In some embodiments thesusceptor temperature is within 100 C or within 50 C of the reactionspace temperature.

According to some embodiments of the present disclosure, the pressure ofthe reaction chamber during processing is maintained at from about 0.01Torr to about 50 Torr, or from about 0.1 Torr to about 10 Torr. In someembodiments the pressure of the reaction chamber is greater than about 6Torr, or about 20 Torr. In some embodiments, a SiOC deposition processcan be performed at a pressure of about 20 Torr to about 500 Torr, about20 Torr to about 50 Torr, or about 20 Torr to about 30 Torr.

In some embodiments a SiOC deposition process can comprise a pluralityof deposition cycles, wherein at least one deposition cycle is performedin an elevated pressure regime. For example, a deposition cycle of aPEALD process may comprise alternately and sequentially contacting thesubstrate with a silicon precursor and a second reactant under theelevated pressure. In some embodiments, one or more deposition cycles ofthe PEALD process can be performed at a process pressure of about 6 Torrto about 500 Torr, about 6 Torr to about 50 Torr, or about 6 Torr toabout 100 Torr. In some embodiments, the one or more deposition cyclescan be performed at a process pressure of greater than about 20 Torr,including about 20 Torr to about 500 Torr, about 30 Torr to about 500Torr, about 40 Torr to about 500 Torr, or about 50 Torr to about 500Torr. In some embodiments, the one or more deposition cycles can beperformed at a process pressure of about 20 Torr to about 30 Torr, about20 Torr to about 100 Torr, about 30 Torr to about 100 Torr, about 40Torr to about 100 Torr or about 50 Torr to about 100 Torr.

Referring to FIG. 4 and according to some embodiments a SiOC thin filmis selectively deposited on a dielectric surface relative to a metalsurface on a substrate in a reaction space by a PEALD process 300comprising at least one cycle comprising:

contacting the substrate with a vapor phase silicon-containing precursorcomprising MPTMS at step 310 such that silicon species adsorb onto thesurface of the substrate;

removing excess silicon-containing precursor and reaction byproducts, ifany, from the substrate surface at step 320;

contacting the substrate with a second reactant comprising H₂ and Arplasma at step 330, thereby converting the adsorbed silicon species intoSiOC;

removing excess second reactant and reaction byproducts, if any, fromthe substrate surface at step 340; and

optionally repeating the contacting and removing steps at step 380 toform a SiOC thin film of a desired thickness and composition.

With continued reference to FIG. 4, the deposited SiOC is treated bycontacting it with an Ar plasma at step 350. The Ar plasma maypreferentially remove SiOC from the metal surface and may also make theSiOC over the metal surface more susceptible to a subsequent etchingprocess. Excess Ar plasma and reaction byproducts, if any, may beremoved from the substrate surface at step 360, for example by shuttingoff the plasma power and continuing to flow the Ar gas. The Ar plasmatreatment may be repeated 390 one, two or more times in sequence. Theplasma treatment step 350 may be included in each deposition cycle ormay be provided intermittently in one or more deposition cycles.

In an optional etching process 370, the substrate may be contacted withan etchant such as a plasma generated in a halide gas. The etchingprocess may remove additional SiOC preferentially from over the metalsurface relative to the dielectric surface. The etching process 370 maybe included in every deposition cycle 300 or intermittently in one ormore deposition cycles.

The deposition cycle 300 is repeated 400 one, two or more times toselectively form a SiOC layer on the dielectric surface relative to themetal surface.

A number of different suitable Si precursors can be used in thepresently disclosed PEALD processes. In some embodiments the suitable Siprecursors may not comprise nitrogen. In some embodiments a suitable Siprecursor may comprise MPTMS. In some embodiments the silicon precursoris a silicon precursor as described in U.S. patent application Ser. No.15/588,026, filed May 5, 2017, which is hereby incorporated by referencein its entirety.

In some embodiments more than one silicon precursor may contact thesubstrate surface at the same time during an ALD phase. In someembodiments the silicon precursor may comprise more than one of thesilicon precursors described herein. In some embodiments a first siliconprecursor is used in a first ALD cycle and a second, different siliconprecursor is used in a later ALD cycle. In some embodiments multiplesilicon precursors may be used during a single ALD phase, for example inorder to optimize certain properties of the deposited SiOC film. In someembodiments only one silicon precursor may contact the substrate duringthe deposition. In some embodiments there may only be one siliconprecursor and one second reactant or composition of second reactants inthe deposition process. In some embodiments there is no metal precursorin the deposition process. In some embodiments the silicon precursor isnot used as a silylating agent. In some embodiments the depositiontemperature and/or the duration of the silicon precursor contacting stepare selected such that the silicon precursor does not decompose. In someembodiments the silicon precursor may decompose during the siliconprecursor contacting step. In some embodiments the silicon precursordoes not comprise a halogen, such as chlorine or fluorine.

In some embodiments, SiOC films are deposited to a thickness of fromabout 3 nm to about 50 nm, from about 5 nm to about 30 nm, from about 5nm to about 20 nm. These thicknesses can be achieved in feature sizes(width) below about 100 nm, about 50 nm, below about 30 nm, below about20 nm, and in some cases below about 15 nm. According to someembodiments, a SiOC film is deposited on a three-dimensional structureand the thickness at a sidewall may be slightly even more than 10 nm. Insome embodiments SiOC films of greater than 50 nm can be deposited. Insome embodiments SiOC films of greater than 100 nm can be deposited. Insome embodiments, SiOC films are deposited to a thickness of more thanabout 1 nm, more than about 2 nm, more than about 3 nm, more than about5 nm, more than about 10 nm.

According to some embodiments SiOC films with differential wet etchrates (WER) may be deposited. In some embodiments, SiOC formed accordingto one or more processes described herein can advantageously demonstratea ratio of a WER of a substantially vertical region to a WER of asubstantially horizontal region of about 1, for example in 0.5 wt % dHF.For example, a ratio of a wet etch rate of a SiOC thin film formed oversubstantially vertical surfaces (e.g., sidewall surfaces) to a wet etchrate of the SiOC thin film formed over substantially horizontal surfaces(e.g., top surfaces) of three-dimensional structures on a substratesurface can be the same or substantially the same. In some embodiments,the ratio can be about 4 to about 0.5, about 2 to about 0.75, about 1.25to about 0.8, or about 1.1 to about 0.9. These ratios can be achieved infeatures with aspect ratios of about 2 or more, about 3 or more, about 5or more or even about 8 or more.

In some embodiments the deposited SiOC thin film may contain up to about40% carbon on an atomic basis (at %). In some embodiments a SiOC filmmay comprise carbon from about 0.1% to about 40%, from about 0.5% toabout 40%, from about 1% to about 30%, or from about 5% to about 20% onan atomic basis. In some embodiments a SiOC film may comprise at leastabout 1%, about 10% or about 20% carbon on an atomic basis.

In some embodiments the deposited SiOC thin film may contain up to about50% silicon on an atomic basis (at %). In some embodiments a SiOC filmmay comprise silicon from about 10% to about 50%, from about 15% toabout 40%, or from about 20% to about 35% on an atomic basis. In someembodiments a SiOC film may comprise at least about 15%, about 20%,about 25% or about 30% silicon on an atomic basis.

In some embodiments the deposited SiOC thin film may contain up to about40% sulfur on an atomic basis (at %). In some embodiments a SiOC filmmay comprise sulfur from about 0.01% to about 40%, from about 0.1% toabout 40%, from about 0.5% to about 30%, or from about 1% to about 20%on an atomic basis. In some embodiments a SiOC film may comprise atleast about 1%, about 10% or about 20% sulfur on an atomic basis. Insome embodiments, the deposited SiOC films do not comprise anappreciable amount of nitrogen. However, in some embodiments a SiOC filmcomprising nitrogen is deposited. In some embodiments, the depositedSiOC films comprises less than about 30 at %, less than about 20 at %,less than about 15 at %, less than about 10 at %, less than about 5 at %of nitrogen, less than about 1 at % nitrogen, or less than about 0.1 at% nitrogen. In some embodiments the SiOC thin films do not comprisenitrogen.

All atomic percentage (i.e., at %) values provided herein excludehydrogen for simplicity and because hydrogen is difficult to accuratelyanalyze quantitatively, unless otherwise indicated. However, in someembodiments, if it is possible to analyze the hydrogen with reasonableaccuracy, the hydrogen content of the films is less than about 20 at %,less than about 10 at % or less than about 5 at %. In some embodimentsthe deposited SiOC thin film may contain up to about 70% oxygen on anatomic basis (at %). In some embodiments a SiOC film may comprise oxygenfrom about 10% to about 70%, from about 15% to about 50%, or from about20% to about 40% on an atomic basis. In some embodiments a SiOC film maycomprise at least about 20%, about 40% or about 50% oxygen on an atomicbasis.

In some embodiments a SiOC film may comprise one or more of SiN, SiO,SiC, SiCN, SiON, SiOSC, SiSC, SiOS, and/or SiOC. In some embodimentsSiOC films deposited according to the disclosed methods do not comprisea laminate or nanolaminate structure.

In some embodiments a SiOC film is not a low-k film, for example a SiOCfilm is not a porous film. In some embodiments a SiOC is a continuousfilm. In some embodiments a SiOC film has a k-value that is less thanabout 10. In some embodiments a SiOC film has a k-value that is lessthan about 7. In some embodiments a SiOC film has a k-values from about2 to about 10. In some embodiments a SiOC film has a k-value that isless than about 5.0, less than about 4.5, less than about 4.3, less thanabout 4.1. In some embodiments a SiOC film has a k-value that from about3.0 to about 7, from about 3.0 to about 5.5, from about 3.0 to about5.0, from about 3.5 to about 4.8, from about 3.5 to about 4.7. In someembodiments a SiOC film has a k-value that is more than the k-value ofany low-k film. In some embodiments a SiOC film has a k-value that ismore than pure SiO₂.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. The described features, structures,characteristics and precursors can be combined in any suitable manner.Therefore, it should be clearly understood that the forms of the presentinvention are illustrative only and are not intended to limit the scopeof the present invention. All modifications and changes are intended tofall within the scope of the invention, as defined by the appendedclaims.

What is claimed is:
 1. A method of selectively forming a siliconoxycarbide (SiOC) thin film on a dielectric surface of a substraterelative to a second surface of the substrate by a plasma enhancedatomic layer deposition (PEALD) process, wherein the PEALD processcomprises at least one deposition cycle comprising: contacting thesubstrate with a first vapor phase silicon reactant; contacting thesubstrate with a second reactant comprising reactive species from afirst plasma generated in a gas that does not comprise nitrogen;contacting the substrate with a second plasma generated in a noble gas;and contacting the substrate with an etchant; and repeating thecontacting steps until a silicon oxycarbide film of a desired thicknesshas been formed on the dielectric surface.
 2. The method of claim 1,wherein the second surface is a metal surface.
 3. The method of claim 1,wherein the second surface comprises TiN, W, Co, Cu, or Ru.
 4. Themethod of claim 1, wherein the dielectric surface comprises SiO₂ or SiN.5. The method of claim 1, wherein the noble gas is Ar gas.
 6. The methodof claim 1, wherein the etchant comprises dilute HF.
 7. The method ofclaim 1, wherein the etchant comprises a plasma generated in a halidegas.
 8. The method of claim 1, wherein the etchant comprises a vaporphase halogen.
 9. The method of claim 1, wherein the reactive speciesare from a plasma generated in a gas that does not comprise nitrogen oroxygen.
 10. The method of claim 9, wherein the gas flows continuouslythroughout the deposition cycle.
 11. The method of claim 1, wherein thesecond reactant comprises reactive hydrogen species.
 12. The method ofclaim 11, wherein the reactive hydrogen species are from hydrogen andargon plasma.
 13. The method of claim 1, wherein the first plasma isgenerated in a gas comprising H₂ and Ar.
 14. The method of claim 13,wherein the first plasma is generated by applying RF power of 5 Watts(W) to about 5000 W to the gas.
 15. The method of claim 1, wherein thefirst vapor phase silicon reactant comprises3-methoxypropyltrimethoxysilane (MPTMS) or bis(triethoxysilyl)ethane(BTESE).
 16. The method of claim 1, wherein the first vapor phasesilicon reactant does not comprise nitrogen.
 17. The method of claim 1,wherein the deposition cycle is carried out at a process temperature ofabout 100° C. to about 300° C.
 18. The method of claim 1, whereincontacting substrate with the first vapor phase silicon reactant andcontacting the substrate with the second reactant are repeated two ormore times in sequence prior to contacting the substrate with the plasmagenerated in a noble gas and the etchant.
 19. A method of selectivelyforming a silicon oxycarbide thin film on a dielectric surface of asubstrate in a reaction space relative to a metal surface of thesubstrate comprising a plurality of deposition cycles, wherein at leastone deposition cycle comprises: contacting the metal and dielectricsurfaces of the substrate with a silicon precursor comprising3-methoxypropyltrimethoxysilane (MPTMS); contacting the metal anddielectric surfaces of the substrate with a first plasma generated in agas that does not comprise nitrogen; contacting the metal and dielectricsurfaces of the substrate with a second plasma generated in argon gas;and contacting the metal and dielectric surfaces of the substrate withan etchant. wherein the deposition cycle is repeated two or more timesto form the SiOC thin film.
 20. The method of claim 19, wherein thefirst plasma is generated in a gas comprising H₂ and Ar.